Evaluation of anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]- guanine (A-5021) in mice

The anti-herpesvirus activity of (1'S,2'R)-9-[[1',2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guani ne (A-5021) was evaluated in murine cells and in several murine models of herpes simplex virus (HSV) infection. Against HSV type 1 (HSV-1), A-5021 was 15-30- and 30-60-fold more active, and against HSV type 2 (HSV-2), it was 2- and 8-fold more active than acyclovir and penciclovir in Balb/3T3 cells, respectively. When antiviral compounds were administered orally (once daily) to mice infected intraperitoneally with HSV-1 (Tomioka), A-5021 was more active than acyclovir or famciclovir in spite of its relatively low oral bioavailability. A-5021 was as active as penciclovir when the antiviral compounds were given intravenously (three times daily) to mice infected intraperitoneally with HSV-2 (186). In mice with a cutaneous HSV-1 (KOS) infection, three times daily oral therapy with A-5021 at 25 mg/kg per day produced more significant reduction in severity of skin lesions than equivalent treatment with acyclovir or famciclovir. In mice infected intracerebrally with HSV-1 (Tomioka), complete survival was observed in the group treated intravenously with A-5021 at 25 mg/kg per day (three times daily), while more than 50% of mice died in the groups treated intravenously with acyclovir of up to 100 mg/kg per day (three times daily). Moreover, A-5021 was more effective than acyclovir in clearing infectious virus from the brain. These findings demonstrate that A-5021 has potent anti-HSV activity in several murine models.

B cell-deficient mice have increased susceptibility to HSV-1 encephalomyelitis and mortality

We studied the susceptibility of B cell-deficient mice to encephalomyelitis following intraperitoneal inoculation of HSV-1. B cell-deficient mice developed striking CNS signs including tail atony, clumsy gait and limb paralysis after HSV-1 infection. In addition, B cell-deficient mice had decreased survival (LD50 = 2.2 x 10(7) PFU) compared to control C57BL/6 mice (LD50 = 2.3 x 10(8) PFU). B cell-deficient mice had encephalomyelitis and detectable virus in the brain 7 days post-infection while C57BL/6 mice did not. Passive transfer of hyperimmune sera protected B cell-deficient mice from death, suggesting a role for antibody in susceptibility to HSV-1 encephalomyelitis.

A herpes simplex virus type 1 latency-associated transcript mutant with increased virulence and reduced spontaneous reactivation

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is essential for efficient spontaneous reactivation of HSV-1 from latency. We previously reported that insertion of the LAT promoter and just the first 1.5 kb of the 8. 3-kb LAT gene into an ectopic location in the virus restored wild-type spontaneous reactivation to a LAT null mutant. This mutant, LAT3.3A (previously designated LAT1.5a), thus showed that the expression of just the first 1.5 kb of LAT is sufficient for wild-type spontaneous reactivation. We also showed that in the context of the entire LAT gene, deletion of LAT nucleotides 76 to 447 (LAT mutant dLAT371) had no effect on spontaneous reactivation or virulence. We report here on a LAT mutant designated LAT2.9A. This mutant is similar to LAT3.3A, except that the ectopic LAT insert contains the same 371-nucleotide deletion found in dLAT371. We found that LAT2.9A had a significantly reduced rate of spontaneous reactivation compared to marker-rescued and wild-type viruses. This was unexpected, since the combined results of dLAT371 and LAT3.3A predicted that spontaneous reactivation of LAT2.9A would be wild type. We also found that LAT2.9A was more virulent than wild-type or marker-rescued viruses after ocular infection of rabbits. This was unexpected, since LAT null mutants and LAT3.3A have wild-type virulence. These results suggest for the first time (i) that regions past the first 1.5 kb of LAT can compensate for deletions in the first 1.5kb of LAT and may therefore play a role in LAT dependent spontaneous reactivation and (ii) that regions of LAT affect viral virulence.

Expression of the first 811 nucleotides of the herpes simplex virus type 1 latency-associated transcript (LAT) partially restores wild-type spontaneous reactivation to a LAT-null mutant

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is required for efficient spontaneous reactivation in the rabbit ocular model. We recently showed that insertion of 1.8 kb of the LAT promoter and the first 1.5 kb of the 8.3-kb primary LAT transcript into a novel, ectopic location in the virus unique long (UL) region restored wild-type spontaneous reactivation to a LAT-null mutant. To further map the LAT spontaneous reactivation function within the first 1.5 kb of LAT, we rescued the same LAT-null mutant by inserting 1.8 kb of the LAT promoter and just the first 811 nucleotides of LAT into the same location in the UL. In a series of three experiments, the resulting virus, designated LAT2.6A, had a spontaneous reactivation rate that was midway between the original LAT-null mutant and wild-type virus. Thus expression of the first 811 LAT nucleotides produced a spontaneous reactivation rate that was significantly higher than that of the LAT-null mutant but significantly less than that of wild type. This suggests that part, but not all, of the LAT function involved in efficient spontaneous reactivation is located within the first 811 nucleotides of the primary 8.3-kb LAT.

In the absence of T cells, natural killer cells protect from mortality due to HSV-1 encephalitis

The importance of natural killer (NK) cells in the resistance to herpes simplex virus type 1 (HSV-1), a common infection of immunocompromised patients, is unclear. Previous data on the role of NK cells in murine HSV-1 infection has been contradictory. Adoptive transfer studies suggested that NK cells mediated resistance to HSV-1, but in vivo depletion approaches demonstrated that NK cells were not important. We studied the course of HSV-1 infection after intranasal (i.n.) inoculation of E26 mice (lacking NK and T cells), T cell knockout (T cell ko) mice (lacking T cells only), or normal control mice. The E26 mice showed greater mortality and an impaired ability to clear virus from lung and brain compared to T cell ko mice and control mice, and had severe necrotizing HSV-1 encephalitis. Therefore, the data support the hypothesis that NK cells play an important role in the natural defense of murine HSV-1 infection.

Recombinant CD40L treatment protects allogeneic murine bone marrow transplant recipients from death caused by herpes simplex virus-1 infection

Posttransplant infection associated with host immune deficiency is the major cause of nonrelapse mortality of human bone marrow transplant recipients. In a new murine model of posttransplant infection, allogeneic bone marrow transplant recipients were infected with herpes simplex virus-1 (HSV-1) via intraperitoneal inoculation 12 weeks after transplantation. Allogeneic transplant recipients with graft-versus-host disease (GVHD) had significantly increased mortality from HSV-1 encephalitis, with deficiencies of both specific anti-HSV-1 antibody and total serum IgG2a. GVHD mice displayed a Th2 cytokine profile (increased interleukin-4 [IL-4] and decreased interferon-gamma) and decreased lipopolysaccharide (LPS) responses, suggesting that both T-cell and B-cell defects contributed to the impaired production of antibody. Because passive transfer of hyperimmune serum protected mice from HSV-1 infection, we hypothesized that CD40 ligand (CD40L), which induces B-cell maturation, would protect mice from HSV-1 infection. CD40L-treated GVHD mice showed elevated IgG2a levels and increased survival compared with vehicle-treated transplant recipients.

Occult herpes family viruses may increase mortality in critically ill surgical patients

BACKGROUND

Effects of cytomegalovirus (CMV) or herpes simplex virus (HSV) infection on surgical intensive care unit (SICU) patients' hospital outcome are unknown.

METHODS

Between July 1, 1994, and September 1, 1995, general SICU patients with persistent sepsis and no bacterial or fungal source identifiable had viral cultures obtained. Patients with positive broncho-alveolar lavage, blood, skin, or sputum cultures for CMV or HSV were studied.

RESULTS

Twenty eligible patients had positive viral cultures during the study period, and 85% of these patients developed subsequent bacterial and/or fungal infections. Mortality was significantly higher following viral infection than in chronic SICU patients (65% vs 35%, P <0.006). Patients with thrombocytopenia complicating their viral infection had significantly higher mortality than those without thrombocytopenia (92% vs 25%, P <0.004).

CONCLUSIONS

At least 14% of critically ill surgical patients have occult infection or reactivation of herpes family viruses. These viruses have known immunosuppressive effects, which may predispose chronic SICU patients to subsequent bacterial and fungal infection, and subsequent organ system failure and death.

Increased levels of IFN-gamma in the trigeminal ganglion correlate with protection against HSV-1-induced encephalitis following subcutaneous administration with androstenediol

Androstenediol (AED) is a metabolic product of dehydroepiandrosterone (DHEA), an adrenal steroid known to possess immunomodulatory characteristics. The present study was undertaken to assess the efficacy of AED treatment in mice ocularly infected with herpes simplex virus type 1 (HSV-1). The subcutaneous administration of 320 mg/kg AED 4 h prior to viral inoculation was found to enhance the survival of HSV-1-infected mice while lower doses (32.0-100.0 mg/kg) were without effect. However, there were no apparent differences in the viral load in the eye or trigeminal ganglion (TG) 3 or 6 days post infection (p.i.) in vehicle- or AED (320 mg/kg)-treated mice. Likewise, there were no differences in the expression of cytokine or chemokine mRNAs in the eyes or TG early (i.e., 3 days p.i.) following infection. However, by 6 days p.i., there was a significant increase in the expression of the chemokines IP-10, MCP-1, and RANTES and the cytokines interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) in the AED (320 mg/kg)-treated mice compared to vehicle-treated controls as determined by reverse transcription (RT)-polymerase chain reaction (PCR) and quantitative PCR (for IFN-gamma). Likewise, there was a corresponding increase in IFN-gamma and IL-2 but not IL-12 protein in the TG of AED-treated mice 6 days p.i. AED-treatment also induced a rise in splenic natural killer activity in a dose- and time-dependent fashion. Collectively, these results suggest that the protective effect following subcutaneous administration of AED is associated in a rise in selective type 1 cytokines (IL-2 and IFN-gamma) as well as natural killer activity.

Stress-related modulation of central nervous system immunity in a murine model of herpes simplex encephalitis

This study assesses the immunomodulatory effects of stress on the pathogenesis of herpes simplex encephalitis (HSE) in a mouse model. Physical restraint served as the stressor and HSE developed subsequent to HSV-1 inoculation into the tongues of subject animals. Clinical data showed that stressed mice lost more weight and had greater mortality rates than unrestrained animals during the course of infection. Histologic tissue sections demonstrated a stress-related reduction of the cellular inflammatory response in the central nervous system (CNS). This model may be useful to further investigate the mechanisms of stress-related immunosuppression in the CNS.

Famciclovir and valaciclovir differ in the prevention of herpes simplex virus type 1 latency in mice: a quantitative study

Famciclovir (FCV) and valaciclovir (VACV) have previously been shown to be potent inhibitors of herpes simplex virus type 1 (HSV-1) in a murine cutaneous model. In the present study, mice were inoculated in the skin of the left ear pinna with herpes simplex virus (HSV) type 1. Antiviral therapy was started on different days postinoculation (p.i.), terminating at the end of day 10 p.i. The compounds were administered twice daily by oral gavage at 50 mg/kg of body weight/dose. Mice were sampled on day 5 p.i., during the acute phase of the infection, and the titers of infectious virus in the target tissues (ear, brain stem, and trigeminal ganglia) were determined. At 2 to 3 months p.i., the ipsilateral and contralateral trigeminal and cervical dorsal root ganglia were explanted, and four different methods were used to detect latent HSV. The methods were (i) conventional explant culture for 5 days followed by homogenization, (ii) long-term culture (up to 73 days) of whole ganglia, followed by homogenization, (iii) dissociation by enzymatic disaggregation and an infectious center assay, and (iv) in situ hybridization to detect latency-associated transcripts (LATs). The conventional explant culture method was the least sensitive method, while in situ staining for LAT was the most sensitive, and all mice, including those treated from early times with FCV, were shown to be latently infected. Significantly less latent virus was detected by all four methods, however, in ganglia obtained from mice that had been treated with FCV in comparison with the amount detected in ganglia from mice that had been treated with VACV. However, in no case was latency completely eliminated.

Neonatal herpes simplex virus infections

Neonatal herpes simplex virus (HSV) infection is one of the life-threatening infections of newborns. It affects approximately 1,500 to 2,200 infants per year in the United States. Changes in the presentation of neonatal HSV infection over the past two decades include an increase in the frequency of skin, eye, and mouth (SEM) disease with a relatively unchanged rate of central nervous system (CNS) disease, but a relative decline in disseminated infection. Although the mortality of neonatal HSV infections has declined with current antiviral therapy, the mortality rate in CNS disease (15%) and disseminated disease (57%) remains high. Morbidity has been seen most frequently in infants with CNS and disseminated disease, with seizures or infection with HSV-2 determined to be risk factors for poor outcome in survivors. In a multicenter, randomized, blinded study by the Collaborative Antiviral Study Group, no differences in outcome were seen between neonates treated with vidarabine and acyclovir. More recently, administration of oral acyclovir has been demonstrated to prevent cutaneous recurrences of HSV after neonatal SEM disease. Although promising, this investigational protocol requires further evaluation before a routine recommendation for prophylactic therapy with oral acyclovir can be made. The application of polymerase chain reaction to rapid diagnosis of neonatal HSV disease may provide additional information on which clinical decisions may be based, but its diagnostic utility outside the research setting is still unproven. Further clinical trials for prophylaxis of recurrent SEM disease, prophylactic therapy for the prevention of recurrences of CNS or disseminated disease, the appropriate use of rapid diagnostic testing, and future therapies that may include passive antibody plus antiviral therapy or higher dosage and longer duration of antiviral therapy need to be evaluated.

Polymerase chain reaction-proved herpes simplex encephalitis in children

OBJECTIVE

To investigate the clinical features in PCR-proved herpes simplex encephalitis (HSE) in children, excluding neonates.

METHODS

We studied the clinical manifestations and laboratory findings of 24 children in whom the diagnosis of herpes infection was confirmed by the PCR assay and compared them with those of 38 children with central nervous system infections other than HSE.

RESULTS

There were no significant differences between groups in the percentage with fever or convulsions, the initial neurologic symptoms or the level of consciousness. Analysis of cerebrospinal fluid showed no significant differences in the cell count or concentration of protein and glucose. Computerized tomography of the brain identified localized abnormalities in 18 (75%) of the 24 HSE patients and in 10 (31%) of the 32 non-HSE patients (P = 0.001). Periodic lateralized epileptiform discharges, abnormal findings on electroencephalography, were detected in 8 (36%) of 22 HSE patients and in none of the non-HSE patients (P = 0.0001). The rates of moderate to severe morbidity and death were significantly higher in the HSE patients than in the non-HSE patients. Of the 9 HSE patients with a Glasgow Coma Scale score > or = 11, all patients recovered completely. HSE patients younger than 3 years of age were more likely to develop severe sequelae or to die of the disorder than older patients (P = 0.02).

CONCLUSIONS

There were no specific clinical characteristics of HSE patients. The results of electroencephalography and computerized tomography were helpful, but not confirmatory, in diagnosing HSE. The Glasgow Coma Scale score and age significantly influenced the mortality and morbidity in the HSE patients.

Exercise, alveolar macrophage function, and susceptibility to respiratory infection

The effects of exercise on susceptibility to respiratory infection were determined by using a murine model of intranasal challenge with herpes simplex type 1 virus (HSV-1). Two doses of treadmill exercise were assessed: moderate short-term (30 min) exercise and prolonged strenuous exercise to voluntary fatigue (2.5-3.5 h). Morbidity and mortality among exercised and control mice were compared after intranasal challenge with HSV-1. We also assessed the ability of alveolar macrophages to restrict HSV-1 viral replication (intrinsic resistance) among exercise and control groups of mice at several time points postexercise. Exercise to fatigue followed by exposure to viral infection resulted in greater morbidity and mortality than either no exercise or short-term moderate exercise. In addition, antiviral resistance of macrophages obtained from the lungs of both exercised groups was suppressed, albeit for a longer duration in the fatigued group. These data are particularly important in that they identify an exercise-induced decrease in antiviral resistance of a specific component of the immune system within the lungs, in conjunction with increased susceptibility to respiratory infection in vivo. The specific mechanism of decreased antiviral resistance of alveolar macrophages and its role in respiratory infection after exercise remains to be determined.

The impact of psychological stress on the efficacy of anti-viral adoptive immunotherapy in an immunocompromised host

Adoptive immunotherapy represents a potentially effective approach by which to control the extent of viral infections in an immunocompromised host. However, the impact of psychological stress and its associated neuroendocrine components on the efficacy of such a treatment strategy has yet to be determined. In the studies described herein, we have developed and utilized a model of primary, local herpes simplex virus (HSV) infection in radiation-induced, immunosuppressed C57BL/6 mice to investigate the role of stress in altering the protective capacity of adoptively transferred lymphocytes that contribute to the resolution of primary HSV infection. The sublethal dose of irradiation chosen for this model was shown to abrogate the local, adaptive immune response to HSV infection as measured by the degree of in vivo lymphoproliferation, development of HSV-specific cytotoxic T lymphocytes (CTL), and production of gamma interferon (IFN-gamma). Both short- and long-term acute stress, applied in the form of physical restraint, diminished the effectiveness of adoptively transferred lymphocytes as was indicated by an enhancement of viral replication in the footpad tissue and an increased rate of mortality. A reduction in the levels of IFN-gamma at the site of primary HSV infection represented at least one mechanism underlying this suppression of anti-viral immunity. Furthermore, the time-dependent restoration of immune function following irradiation was shown to be compromised in mice subjected to the restraint stress procedure. Together, these findings emphasize the potential role of psychological stress in suppressing both the capability of adoptive immunotherapeutic procedures to combat viral infection and the reestablishment of immune function in individuals who have undergone immunosuppressive therapy.

The acquisition of herpes simplex virus during pregnancy

BACKGROUND

The acquisition of genital herpes during pregnancy has been associated with spontaneous abortion, prematurity, and congenital and neonatal herpes. The frequency of seroconversion, maternal symptoms of the disease, and the timing of its greatest effect on the outcome of pregnancy have not been systematically studied.

METHODS

We studied 7046 pregnant women whom serologic tests showed to be at risk for herpes simplex virus (HSV) infection. Serum samples obtained at the first prenatal visit, at approximately 16 and 24 weeks, and during labor were tested for antibodies to HSV types 1 and 2 (HSV-1 and HSV-2) by the Western blot assay, and the results were correlated with the occurrence of antenatal genital infections.

RESULTS

Ninety-four of the women became seropositive for HSV; 34 of the 94 women (36 percent) had symptoms consistent with herpes infection. Women who were initially seronegative for both HSV-1 and HSV-2 had an estimated chance of seroconversion for either virus of 3.7 percent; those who were initially seropositive only for HSV-1 had an estimated chance of HSV-2 seroconversion of 1.7 percent; and those who were initially HSV-2-seropositive had an estimated chance of zero for acquiring HSV-1 infection. Among the 60 of the 94 pregnancies for which the time of acquisition of HSV infection was known, 30 percent of the infections occurred in the first trimester, 30 percent in the second, and 40 percent in the third. HSV seroconversion completed by the time of labor was not associated with an increase in neonatal morbidity or with any cases of congenital herpes infection. However, among the infants born to nine women who acquired genital HSV infection shortly before labor, neonatal HSV infection occurred in four infants, of whom one died.

CONCLUSIONS

Two percent or more of susceptible women acquire HSV infection during pregnancy. Acquisition of infection with seroconversion completed before labor does not appear to affect the outcome of pregnancy, but infection acquired near the time of labor is associated with neonatal herpes and perinatal morbidity.

Differences in resistance to herpes simplex virus type 1 (HSV-1) among oligodendroglia derived from different strains of mice are determined after viral adsorption but prior to the expression of immediate early (IE) genes

The nature of an innate cellular resistance to HSV-1 of cultured murine oligodendrocytes (OLs) in three strains of mice (C57BL/6J, Balb/cByJ and A/J) was investigated. The expression of immediate early (ICP4), early (ICP8) and late (gC) antigens in primary OL cultures was studied using an indirect immunofluorescence (IF) technique. HSV-1 infected OLs from C57BL/6J mice showed no viral antigens at 24 h post infection (p.i.) but rather a marked delay in antigen expression beginning at 60 h p.i. In contrast all three proteins were expressed in A/J OLs at 24 h p.i. while Balb/cByJ OLs showed an intermediate protein expression pattern. These results suggest that the innate cellular resistance to HSV-1 is determined prior to the expression of immediate early viral antigens. To further study these differences, the adsorption capacity between the three mouse strains was compared using dextran purified, [3H]thymidine labelled virus. No differences in HSV-1 adsorption were identified. Results from viral penetration studies approached statistical significance suggesting that penetration may be impaired in C57BL/6J and Balb/cByJ OLs when compared to A/J OLs and is likely fusion independent. The selective differences in HSV-1 resistance mediated by OLs, reflect differences in virus host cell interactions, that likely contribute to differences in mortality, viral spread, and the ability of virus to induce central nervous system (CNS) demyelination.

Highly virulent strains of herpes simplex virus fail to kill mice following infection via gingival route

Virulence of herpes simplex virus (HSV) in mice has been demonstrated to be dependent on the site of infection. In this experiment, pathogenesis of HSV was studied in 2 different routes of infection in a mouse model system. When BALB/c mice were infected with 5 x 10(3) plaque-forming units (PFU) of virulent HSV type 1 Miyama GC+ strain (HSV-1-GC+) intraperitoneally, all mice were dead in 6 to 9 days. HSV-1-GC+ was recovered from organs such as the cerebrum, cerebellum, brainstem, and spleen 2 to 5 days after infection, but not from other organs such as trigeminal ganglia. However, if mice were infected in the maxillary gingiva with 1.0 x 10(7) PFU of HSV-1-GC+, all mice survived. HSV-1-GC+ was recovered from the trigeminal ganglia and brainstem 2 to 5 days after infection, but not from other organs tested. When mice were infected in maxillary gingiva with HSV-1-GC+, followed by the intraperitoneal injection of 6 mg of cyclophosphamide 72 hrs after virus infection, all mice were dead within days. Immunofluorescent and hematoxylin-eosin staining of gingival tissue sections revealed that when mice were infected in maxillary gingiva with HSV-1-GC+, 3 times as many gamma delta T-cells and 5 times as many polymorphonuclear cells can be detected in sections of maxillary gingiva when compared with non-infected mice. These data show that the gingiva of mice is considerably more resistant to infection with HSV, compared with the peritoneal cavity, and suggest the possible presence of an oral defense mechanism which might be different from that in the peritoneal cavity.

Differential effects of famciclovir and valaciclovir on the pathogenesis of herpes simplex virus in a murine infection model including reactivation from latency

The ability of famciclovir and valaciclovir to affect the establishment and maintenance of latency in mice with a cutaneous herpes simplex type 1 (HSV-1) infection was examined. Mice were treated via drinking water starting at various times between days 1 and 5 and terminating on day 10 after inoculation. Clinical signs and viral replication in the target tissues were monitored. Three to four months later, trigeminal and dorsal root ganglia were explanted from groups of 16 mice and examined for latent virus by cocultivation. The two compounds differed in their effects on the acute neural infection, and ganglia explanted from famciclovir-treated mice were markedly reduced in their ability to reactivate virus, although neither drug affected latency if treatment was delayed for several months. The difference between the compounds is likely to reflect differences in the metabolism of their respective products, penciclovir and acyclovir, in infected neurons.

Effect of antibody alone and combined with acyclovir on neonatal herpes simplex virus infection in guinea pigs

Neonatal herpes simplex virus (HSV) infection produces severe disease with unacceptable morbidity and mortality with current antiviral therapies. The effect of therapy with passive anti-HSV antibody and acyclovir was evaluated using a guinea pig model of neonatal HSV. Newborn animals were inoculated intranasally and treated with acyclovir (60 mg/kg/day) or antibody (or both), beginning on days 0, 2, or 3 after HSV-2 inoculation. Acyclovir alone was effective only when begun on day 0, and antibody alone was effective when begun on or before day 2. Only combination therapy was effective on day 3, reducing mortality from 82% (14/17) in controls to 44% (7/16; P < .05). Combined therapy also significantly reduced the duration of skin, eye, and mouth disease and respiratory symptoms but not recurrent disease. These data suggest that addition of antibody therapy to acyclovir may improve the outcome of neonatal HSV disease.

Herpes simplex encephalitis

Herpes simplex encephalitis (HSE) is a life-threatening condition with high mortality as well as significant morbidity in survivors. In most cases herpes simplex virus type 1 (HSV-1) is responsible for the diseases, however, the type 2 virus (HSV-2) is involved in 4-6% of cases. Primary HSV infection is identified in only one-third of patients with HSE. The majority of cases are recorded in adults with recurrent HSV infection who are already seropositive for HSV at the onset of symptoms, but only 6-10% of these patients have a history of labial herpes. Acute focal, necrotizing encephalitis with inflammation and swelling of the brain tissue are consistent features of the pathology of HSE. HSV-induced cytolysis certainly damages neurones, oligodendrocytes and astrocytes, but the role of cellular and humoral immunopathology is important. A complex network of cytokines seems to be active in regulating the local immune response and inflammation during and after HSE. Brain biopsy, serological analysis of intrathecal HSV antibodies and detection of HSV-DNA in the cerebrospinal fluid (CSF) are all useful techniques to confirm the aetiology of HSE. Neurodiagnostic tests which support a presumptive diagnosis of HSE include: CSF analysis, electroencephalography, computer-assisted tomography and magnetic resonance imaging. Although aciclovir is the treatment of choice in HSE, mortality and morbidity still remain problematic. Long-term follow-up indicates that intrathecal cellular and humoral activation persist in HSE.

CD8+ type-2 T cells enhance the severity of acute herpes virus infection in mice

The role of CD8+ suppressor T cells in acute herpes simplex virus type 1 (HSV) infection was investigated in mice. CD8+ CD11b+ TCR-gamma/delta + suppressor T cells (HSV-STC) were demonstrated in spleens of mice infected intraperitoneally (i.p.) with HSV. When HSV-STC from mice infected with a 10 LD50 of HSV (donors) were adoptively transferred to mice 3 days after being infected with a 1 LD50 dose of HSV (recipients), the morbidity and mortality of recipients were greatly increased (mean survival time in days (MSD): 9.4 days; mortality, 100%) as compared with controls that received CD4+ T cells or a whole T-cell lysate from donors (MSD, > 19.6 days or > 19.1 days; mortality, 38% or 50%). The morbidity and mortality of mice exposed to a 1 LD50 of HSV were also increased when they were continuously treated with recombinant murine IL-4. However, the survival rate of mice exposed to a 10 LD50 of HSV increased after multiple treatments of these mice with anti-IL-4 monoclonal antibody. IL-4-producing cells were detected in a population of HSV-STC, and IL-4 was produced when these cells were cultured in the presence of UV-inactivated HSV in vitro. These results indicate that IL-4 plays an important role in the progression of acute HSV infection and, through the production of IL-4, HSV-STC may increase the severity of the acute-phase infection of HSV in mice.

Cytokine-mediated survival from lethal herpes simplex virus infection: role of programmed neuronal death

The mechanisms responsible for cytokine-mediated antiviral effects are not fully understood. We approached this problem by studying the outcome of intraocular herpes simplex (HSV) infection in transgenic mice that express interferon gamma in the photoreceptor cells of the retina. These transgenic mice showed selective survival from lethal HSV-2 infection manifested in both eyes, the optic nerve, and the brain. Although transgenic mice developed greater inflammatory responses to the virus in the eyes, inflammation and viral titers in their brains were equivalent to nontransgenic mice. However, survival of transgenic mice correlated with markedly lower numbers of central neurons undergoing apoptosis. The protooncogene Bcl2 was found to be induced in the HSV-2-infected brains of transgenic mice, allowing us to speculate on its role in fostering neuronal survival in this model. These observations imply a complex interaction between cytokine, virus, and host cellular factors. Our results suggest a cytokine-regulated salvage pathway that allows for survival of infected neurons.

Neonatal herpes simplex: clinical findings and outcome in relation to type of maternal infection

In 39 mothers of children with neonatal herpes simplex virus infection, maternal infection was serologically characterized retrospectively and was related to maternal clinical symptoms and to the clinical findings and outcome in the child. Thirteen mothers had a primary infection (six type 1, seven type 2), mostly with clinical symptoms. The mean age of onset of the disease of the infants was 7 days and a disseminated disease was most commonly found. Most of the type 1-infected children recovered completely, whereas all but one of the type 2-infected children died. Twenty mothers had a recurrent (2 type 1, 18 type 2) and 4 an intermediate infection (primary type 2, prior infection with type 1), mostly asymptomatic. Their children had a localized disease (of the skin-eye-mouth or the central nervous system) with onset at a mean age of 14 or 13 days, respectively. The frequency of neurological sequelae was high. Two mothers had no serological signs of herpes infection.

[Herpes simplex infection in pregnant women and newborn infants]

The incidence of genital herpes infection is increasing. About 50% of infections in women are asymptomatic. Neonatal infection is the most serious complication of genital HSV-infection, the mortality being 70% if untreated. The incidence of asymptomatic HSV-infection in pregnant women at the time of giving birth is 0.2%. These women cannot be identified on the basis of clinical symptoms and medical history, and the diagnostic methods currently in use are not sufficiently sensitive for the screening of low risk groups. Pregnant women with primary HSV-infection shed larger quantities of virus than women with recurrent infection, furthermore the foetus has not received passive immunisation by maternal antibody transfer. There is an increased risk of miscarriage, intrauterine infection and premature birth in connection with primary HSV-infection in pregnancy. Almost 50% of children born to mothers with primary HSV-infection at the time of birth become infected neonatally, compared with only 2-5% of children born to mothers with active recurrent HSV-infection. Recommendations are given for monitoring primary HSV-infection in the third trimester with viral cultures, monitoring recurrent HSV-infections clinically and indications for when delivery should be by caesarean section. Children born to women with active primary HSV-infection should be treated with antiviral agents. Children born to women with recurrent infection should have their secretions cultured for HSV.